Circuit device and method of manufacture thereof

ABSTRACT

A circuit device  10  comprises conductive patterns  11 , separated by separation grooves  41 , circuit elements  12 , affixed onto conductive patterns  11 , and an insulating resin  13 , covering circuit elements  12  and conductive patterns  11  and filling separation grooves  41  while exposing the rear surfaces of conductive patterns  11 . Constricted parts  19  are formed at side surfaces of separation grooves  41 . At constricted parts  19 , the width of separation grooves  41  is made narrower than at other locations. Thus by making insulating resin  13  adhere closely to constricted parts  19 , the adhesion of insulating resin  13  with conductive patterns  11  is improved.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a circuit device and a method ofmanufacture thereof and particularly relate to a circuit device, withwhich separation grooves having constricted parts at side surfaces areformed by performing etching a plurality of times on a copper foil toform the separation grooves and the transient thermal resistance isrestrained by forming conductive patterns thickly, and a method ofmanufacture of such a circuit device.

[0003] 2. Description of the Related Art

[0004] Conventionally, due to being employed in portable telephones,portable computers, etc., circuit devices that are set in electronicequipment have been demanded to be compact, thin, and lightweight.

[0005] Recently, as general semiconductor devices called CSP's (chipsize packages), wafer-scale CSP's of sizes equivalent to chips and CSP'sof sizes slightly larger than chips have been developed.

[0006]FIG. 14 shows a CSP 66, which is slightly larger than a chip sizeand employs a glass epoxy substrate 5 as the supporting substrate. Here,a description shall be provided for the case where a transistor chip Tis mounted onto glass epoxy substrate 65.

[0007] On the surface of this glass epoxy substrate 65, a firstelectrode 67, a second electrode 68, and a die pad 69 are formed. Afirst rear surface electrode 70 and a second rear surface electrode 71are formed on the rear surface of this glass epoxy substrate 65. Viathrough holes TH, the abovementioned first electrode 67 is electricallyconnected with first rear surface electrode 70 and second electrode 68is electrically connected with second rear surface electrode 71. Theabove-mentioned transistor chip T is affixed in bare form onto die pad69, the emitter electrode of the transistor is connected via a metalwire 72 to first electrode 67, and the base electrode of the transistoris connected via a metal wire 72 to second electrode 68. Furthermore, aresin layer 73 is provided on glass epoxy substrate 65 so as to covertransistor chip T.

[0008] Though employing a glass epoxy substrate 65, the abovementionedCSP 66, unlike a wafer-scale CSP, has the merits of being simple in theextension structure from chip T to the rear surface electrodes 70 and 71for external connection and being inexpensive to manufacture.

[0009] However, the above-described CSP 66 uses a glass substrate 65 asan interposer and this places on limit on making CSP 66 more compact andthinner. A circuit device 80, with which such a mounting substrate ismade unnecessary as shown in FIG. 15, has thus been developed.

[0010] As shown in FIG. 15, circuit device 80 comprises conductivepatterns 81, circuit elements 82 affixed onto conductive patterns 81,metal wires 84, electrically connecting circuit elements 82 andconductive patterns 81, and an insulating resin 83, covering circuitelements 82 and conductive patterns 81 while exposing the rear surfacesof conductive patterns 81. Circuit device 80 is thus arranged so that amounting substrate is unnecessary and is formed more thinly and morecompactly in comparison to CSP 66.

[0011] However, with the above-described circuit device 80, conductivepatterns 81 are formed thinly and have a thickness of only approximately40 μm, and since this causes increase of the transient thermalresistance, there was the problem that temperature rise of circuitdevice 80 occurs quickly due to heat generation by circuit elements 82.Also, if thick conductive patterns 81 are formed by forming separationgrooves by a single time of etching, the separation grooves are formedto be wide in width, causing decrease of the effective area in whichconductive patterns 81 are formed.

[0012] Furthermore, though side surfaces of conductive patterns 81 areformed to a curved form due to conductive patterns 81 being formed byetching, the adhesion with insulating resin 13 was not adequate andthere was the problem that conductive patterns 81 peeled off frominsulating resin 13.

[0013] This embodiments of present invention has been made in view ofthe above problems. One of objects of this embodiments of presentinvention is to provide a circuit device, having conductive patternsthat are formed thickly in order to make the transient thermalresistance small, and a method of manufacturing such a circuit device.Another object of this invention is to provide a circuit device, withwhich the adhesion of an insulating resin with conductive patterns isimproved by the provision of constricted parts at side surfaces ofseparation grooves that separate the conductive patterns.

SUMMARY OF THE INVENTION

[0014] The preferred embodiment of this invention firstly provides acircuit device comprising: conductive patterns separated by separationgroove; circuit element, affixed onto the conductive pattern; and aninsulating resin, covering the circuit elements and the conductivepatterns and filling the separation grooves while exposing the rearsurfaces of the conductive patterns; wherein constricted part is formedat side surface of the separation groove and the insulating resin isadhered to the constricted part. By forming constricted parts at theseparation grooves, the adhesion of the conductive patterns with theinsulating resin that fills the separation grooves can be improved.

[0015] The preferred embodiment of this invention secondly provides acircuit device comprising: conductive patterns separated by separationgroove; circuit element, affixed onto the conductive pattern; and aninsulating resin, covering the circuit element and the conductivepatterns and filling the separation groove while exposing the rearsurfaces of the conductive patterns; wherein the separation groove isformed of a plurality of grooves formed by etching a plurality of times.By thus forming separation grooves by a plurality of times of etching,the separation grooves can be formed deeply while being made as narrowin width as possible and the conductive patterns can be formed thickly.

[0016] The preferred embodiment of this invention thirdly provides acircuit device manufacturing method comprising: forming conductivepatterns by forming separation grooves at locations of a conductive foilexcept locations that are to be the conductive patterns; positioningcircuit element on the conductive pattern; and forming an insulatingresin so as to cover the circuit element and fill the separation groove;wherein constricted part is formed on side surfaces of the separationgrooves by a plurality of times of etching and the insulating resin isadhered to the constricted part.

[0017] The preferred embodiments of this invention provides thefollowing effects.

[0018] Firstly, by forming separation grooves 41, which separateconductive patterns 11, by etching a plurality of times, constrictedparts 19 can be formed in separation grooves 41. Thus by close adhesionof insulating resin 13, which seals the entirety, with constricted parts19, the force of adhesion of conductive patterns 11 with insulatingresin 13 can be improved.

[0019] Secondly, by forming separation grooves 41 by etching a pluralityof times, separation grooves 41, with which the length in the depthdirection is greater than that in the width direction, can be formed.Conductive patterns 11 can thus be formed thickly without spreading thewidth of separation grooves 41. The mounting density of the circuitdevice can thus be improved.

[0020] Thirdly, by forming conductive patterns 11 thickly, the transientthermal resistance can be made low and the heat radiation effect of thecircuit device can be improved.

[0021] Fourthly, in the step of forming separation grooves 41, a commonmask 30 can be used to perform exposure of first resist PR1 and secondresist PR2. Separation grooves 41 having constricted parts 19 providedat the side surfaces can thus be formed without having to prepare masksseparately.

BRIEF DESCRIPTION OF THE DRAWINGS

[0022]FIG. 1 is a plan view (A), a sectional view (B), and an enlargedsectional view (C) showing a circuit device of the preferred embodiment.

[0023]FIG. 2 is a plan view (A) and a sectional view (B) showing acircuit device of the preferred embodiment.

[0024]FIG. 3 is a characteristics diagram showing the thermal resistancevalues of a circuit device of the preferred embodiment.

[0025]FIG. 4 is a sectional view (A) and a plan view (B) showing acircuit device manufacturing method of the preferred embodiment.

[0026]FIG. 5 is a sectional view (A) and a sectional view (B) showing acircuit device manufacturing method of the preferred embodiment.

[0027]FIG. 6 is a sectional view (A) and a plan view (B) showing acircuit device manufacturing method of the preferred embodiment.

[0028]FIG. 7 is a sectional view (A), a sectional view (B), and asectional view (C) showing a circuit device manufacturing method of thepreferred embodiment.

[0029]FIG. 8 is a sectional view (A), a sectional view (B), and asectional view (C) showing a circuit device manufacturing method of thepreferred embodiment.

[0030]FIG. 9 is a sectional view (A) and a plan view (B) showing acircuit device manufacturing method of the preferred embodiment.

[0031]FIG. 10 is a sectional view showing a circuit device manufacturingmethod of the preferred embodiment.

[0032]FIG. 11 is a sectional view showing a circuit device manufacturingmethod of the preferred embodiment.

[0033]FIG. 12 is a sectional view showing a circuit device manufacturingmethod of the preferred embodiment.

[0034]FIG. 13 is a plan view showing a circuit device manufacturingmethod of the preferred embodiment.

[0035]FIG. 14 is a sectional view showing a related-art circuit device.

[0036]FIG. 15 is a sectional view showing a related-art circuit device.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0037] (First Embodiment for Describing a Configuration of a CircuitDevice)

[0038] As shown in FIG. 1, a circuit device 10 comprises conductivepatterns 11, separated by separation grooves 41, circuit elements 12,affixed onto conductive patterns 11, and an insulating resin 13,covering circuit elements 12 and conductive patterns 11 and fillingseparation grooves 41 while exposing the rear surfaces of conductivepatterns 11; and is arranged with constricted parts 19 being formed atside surfaces of separation grooves 41 and insulating resin 13 beingclosely adhered to constricted parts 19. This configuration shall now bedescribed in detail.

[0039] The material of conductive patterns 11 is selected inconsideration of brazing material attachment property, bonding property,and plating property, and as this material, a conductive foil having Cuas the principal material, a conductive foil having Al as the principalmaterial, or a conductive foil formed of an alloy, such as Fe—Ni, etc.,is employed. Here, a configuration in which conductive patterns 11 areembedded in insulating resin 13 with their rear surfaces exposed andelectrically separated by separation grooves 41 is realized. Also at thefour corners of circuit device 10, land-form conductive patterns 11,onto which circuit elements 12 are mounted, are formed and conductivepatterns 11, serving as bonding pads for metal wires 14, are formed inbetween. Also, at the rear surfaces of conductive patterns 11 that areexposed from insulating resin 13 are provided external electrodes 15formed of soft solder or other brazing material. Conductive patterns 11are formed by etching and the side surfaces thereof are formed to curvedsurfaces, each provided with a protrusion at an intermediate part.Locations of the rear surface of the device at which external electrodes15 are not provided are covered by a resist 16. Here, conductivepatterns 11 are formed to be 140 μm or more in thickness.

[0040] Semiconductor elements, such as transistors, diodes, IC chips,etc., and passive elements, such as chip capacitors, chip resistors,etc., may be cited as examples of circuit elements 12. Though thethickness will be greater, face-down semiconductor elements, such asCSP's, BGA's, etc., may also be mounted. Circuit elements 12 that aremounted here in face-up manner are electrically connected via metalwires 14 to other conductive patterns 11.

[0041] Insulating resin 13 covers circuit elements 12, metal wires 14,and conductive patterns 11 while exposing the rear surfaces ofconductive patterns 11. As insulating resin 13, a thermosetting resin ora thermoplastic resin may be employed. Also, separation grooves 41,which separate the respective conductive patterns 11, are filled withinsulating resin 13. Furthermore, the circuit device 10 of the preferredembodiment is supported in its entirety by insulating resin 13.

[0042] Separation grooves 41 are formed between the respectiveconductive patterns by a plurality of times of etching and haveconstricted parts 19 formed at their intermediate parts. The width inthe lateral direction of constricted parts 19 are formed narrower thanthe other locations of separation grooves 41. Thus by insulating resin13 adhering closely to constricted parts 19, since the side surfaces ofconstricted parts 41 correspond to the side surfaces of conductivepatterns 11, the strength of adhesion of conductive patterns 11 withinsulating resin 13 can be improved. As mentioned above, separationgrooves 41 are formed by etching the same locations of the conductivefoil, which is the material of conductive patterns 11, a plurality oftimes. Separation grooves 41 are thus made greater in their depth thanin their width. Also, constricted parts 19 are formed continuouslyacross all side surfaces of separation grooves 11.

[0043] Now referring to FIG. 1(B), since separation grooves 41 areformed by etching twice, separation grooves 41 are formed so that theirdepth is approximately twice their width. In a case where separationgrooves 41 are formed by etching an even greater number of times, theirdepth can be made even greater than their width. Also, since thethickness of conductive patterns 11 correspond to the depth ofseparation grooves 41, conductive patterns 11 that are formed to bethicker than the width of the separation grooves can be formed by thepreferred embodiment.

[0044]FIG. 1(C) is an enlarged sectional view of a location at which aseparation groove 41 of FIG. 1(B) is formed. The details of separationgroove 41 shall now be described with reference to FIG. 1(C). With thepreferred embodiment, a separation groove 41 is formed by performingetching a plurality of times. A separation groove 41 is thus formed bytwo times or more of etching, and as the number of times etchingincreases, the number of constricted parts 19 formed at the side partsof separation groove 41 increases as well.

[0045] In the case where a separation groove 41 is formed by two timesof etching, separation groove 41 is formed of a first separation groove41A, formed by the first time of etching, and a second separation groove41B, formed by the second time of etching. Here, second separationgroove 41B is formed to be greater in cross-sectional area than firstseparation groove 41A. Thus by constricted part 19 being formed near theupper part of separation groove 41, the side surfaces of conductivepatterns 11 that are formed of first separation groove 41A protrude intoseparation groove 41 in an eaves-like form into separation groove 41.The adhesion of conductive patterns 11 and insulating resin 13, filledin separation groove 41, is thus improved by the anchor effect betweenthese components.

[0046] Referring now to FIG. 2, the configuration of circuit device 10of another form shall be described. The basic arrangement of circuitdevice 10 described here is the same as that shown in FIG. 1, thedifference being that conductive patterns 11 are exposed in a protrudingmanner from the rear surface of the insulating resin. Here, the rearsurfaces and parts of the side surfaces of conductive patterns 11 areexposed from insulating resin 13. Conductive patterns 11 can thus beformed even more thickly than the circuit device shown in FIG. 1.Specifically, conductive patterns 11 can be formed to be 250 μm to 300μm in thickness. The thermal radiation effect of conductive patterns 11can thus be improved.

[0047] Referring now to FIG. 3, the results of conducting an experimentcomparing the transient thermal resistance using a related-art circuitdevice 80 and this circuit device 10 of this embodiment shall now bedescribed. The abscissa axis of this graph indicates the powerapplication time in logarithmic scale and the ordinate axis indicatesthe measured thermal resistance. The power application time indicated bythe abscissa axis indicates the duration during which power is suppliedto a circuit device, and the thermal resistance indicated by theordinate axis indicates the degree of temperature rise when power issupplied. That the thermal resistance is low thus indicates that theheat radiating property of the circuit device is excellent.

[0048] The dotted line indicates the experimental results for therelated-art type circuit device 80, which is shown in FIG. 15 and hasconductive patterns 81 formed to a thickness of approximately 50 μm. Thesolid line indicates the experimental results for the circuit device 10of preferred embodiment, having conductive patterns 11 formed to athickness of approximately 140 μm.

[0049] The experimental results for the related-art circuit deviceindicate that the thermal resistance rises rapidly at a powerapplication time of approximately 1 second and levels off at 180° C./Wat 10 seconds and onwards. The experimental results for circuit device10 of preferred embodiment, having thickly formed conductive patterns11, indicate that the thermal resistance remain at values lower thanthose of the related art. In particular, the thermal resistance valuefor the preferred embodiment is approximately 30% lower than that of therelated art at a power application time of approximately 10 seconds. Theabove shows that the circuit device 10 of preferred embodiment, havingthickly formed conductive patterns 11, provides the merit of being lowerin transient thermal resistance in comparison to the related art.

[0050] (Second Embodiment for Describing a Circuit Device ManufacturingMethod)

[0051] A method of manufacturing circuit device 10 shall now bedescribed with reference to FIG. 4 to FIG. 13. A circuit devicemanufacturing method of this embodiment comprises the steps of formingconductive patterns 11 by forming separation grooves 41 at locations ofa conductive foil besides locations that are to be conductive patterns11, positioning circuit elements 12 on conductive patterns 11, andforming insulating resin 13 so as to cover circuit elements 12 and fillseparation grooves 13, and forming constricted parts 19 on side surfacesof separation grooves 41 by forming separation grooves 41 by a pluralityof times of etching and closely adhering insulating resin 13 toconstricted parts 19. The following shall describe the above-describedrespective steps in detail.

[0052] As shown in FIG. 4 to FIG. 8, in the first step of thisembodiment, a conductive foil 40 is prepared, and by performing etchinga plurality of times, separation grooves 41 provided with constrictedparts 19 are formed.

[0053] In this step, first, a sheet-form conductive foil 40 is preparedas shown in FIG. 4(A). The material of this conductive foil 40 isselected in consideration of brazing material attachment property,bonding property, and plating property, and as this material, aconductive foil having Cu as the principal material, a conductive foilhaving Al as the principal material, or a conductive foil formed of analloy, such as Fe—Ni, etc., is employed.

[0054] The thickness of the conductive foil is preferably approximately10 μm to 300 μm in consideration of subsequent etching. Specifically, asshown in FIG. 4(B), four to five blocks 42, on which a plurality ofmounting parts will be formed, are aligned in a spaced manner alongconductive foil 40 of strip-like form. Between each block are providedslits 43 for absorbing the stress that arises in conductive foil 40 in aheating process in the molding step, etc. Also, index holes 44 areprovided at fixed intervals at the upper and lower peripheral edges ofconductive foil 40 and these are used for positioning in the respectivesteps.

[0055] Next, conductive patterns 11 are formed in each block. First asshown in FIG. 5, a first resist PR1, which is an etch-resistant mask, isformed and photoresist PR1 is patterned so that conductive foil 40 isexposed at regions except the regions that are to become conductivepatterns 11.

[0056] Specifically, as shown in FIG. 5(A), first resist PR1 is formedover the entire top surface of conductive foil 40 in which conductivepatterns 11 are to be formed. Then using a mask 30, exposure of thefirst resist is performed at locations at which separation grooves 41are to be formed. Specifically, a light blocking material 31 is formedat locations of mask 30 that correspond to locations that are to becomeconductive patterns 11 and openings 32, at which light blocking material31 is not provided, are formed at locations at which separation grooves41 are to be formed. Thus by illuminating light that progresses parallelto conductive foil 40 from above mask 30, first resist PR1 is exposedjust at the locations at which separation grooves 41 are to be formed.Here, if the width of an opening formed at the mask is W1, the openingprovided in resist PR1 will also be formed to have the width W1.

[0057] Referring now to FIG. 5(B), by performing a development process,first resist PR1 is removed just at the exposed locations and the topsurface of conductive foil 40 becomes exposed at locations at whichseparation grooves 41 are to be formed. Separation grooves 41 are thenformed by etching. The separation grooves 41 that are formed by etchinghave a depth, for example, of 50 μm and the side surfaces thereof arerough surfaces and are thus improved in adhesion to insulating resin 13.

[0058] As the etchant used here, ferric chloride or cupric chloride ismainly employed, and the abovementioned conductive foil is dipped inthis etchant or is showered with this etchant. Since generally with wetetching, etching is performed in a non-anisotropic manner, the sidesurfaces become curved structures.

[0059] Referring now to FIG. 6(A), the section on which etching has beenperformed shall be described. Since the etching removes conductive foil40 in an isotropic manner, the width W2 of separation groove formed byetching is made greater than the width W1 of the openings of firstresist PR1. Also, the width W1 of the openings of first resist PR1 isthe same as the width W1 of the mask for performing exposure. It canthus be understood that the width W2 of the openings of separationgrooves 41 is made greater than the width W1 of the mask for performingexposure.

[0060] Specific conductive patterns 11 are shown in FIG. 6(B). In thisfigure, conductive patterns corresponding to one of blocks 42 shown inFIG. 4(B) are shown in an enlarged manner. A region surrounded by dottedlines is one mounting part 45 in which conductive patterns 11 arearranged, and on one block 42, a plurality of mounting parts 45 arealigned in the form of a matrix, and the same conductive patterns 11 areformed at each mounting part 45.

[0061] Referring now to FIG. 7, a method by which constricted parts 19are formed by etching separation grooves 41 further shall be described.

[0062] As shown in FIG. 7(A), after peeling and removing first resistPR1, a second resist PR2 is formed on the top surface of conductive foil40, including the top surfaces of separation grooves 41. Then using thesame mask 30 as the mask used on first resist PR1, exposure of secondresist PR2 is carried out. As mentioned above, the width W2 of theopenings of separation grooves 41 is made wider than the opening widthW1 of openings 32 provided in mask 30. Thus when second resist PR2 isexposed using mask 30, though the second resist PR2 near the bottomparts of separation grooves 41 will be exposed, the second resist PR2 atside surfaces of separation grooves 11 will not be exposed.

[0063] Second resist PR2, which has been exposed as described above, isthen subject to a development process as shown in FIG. 7(B). The secondresist PR2 that is formed at the side surfaces of separation grooves 11,which are not exposed, thus remains. Second resist PR2 thus covers thetop surface of conductive foil 40 while leaving just the vicinities ofthe bottom parts of separation grooves 41 exposed.

[0064] Etching is then performed to form constricted parts 19 as shownin FIG. 17. By the etching progressing in an isotropic manner from theexposed bottom surfaces of separation grooves 41, separation grooves 41are formed deeply and constricted parts 19 are formed near theintermediate parts in the depth direction of the separation grooves. Bythus forming the separation grooves by a plurality of times of etching,constricted parts 19 of narrowly formed width can be formed.Furthermore, deep separation grooves of a width equivalent to separationgrooves formed by one time of etching can be formed. Conductive patterns11 can thus be formed thickly without widening the width of separationgrooves 41. Second resist PR2 is removed after separation grooves 41have been formed.

[0065] Furthermore, though in the above description, the exposure offirst resist PR1 and the exposure of second resist PR2 were performedusing the same mask, second resist PR2 may instead be exposed using amask 30 with narrowly formed openings 32.

[0066] Referring now to FIG. 8, a method of performing etching againusing just first resist PR1 shall be described. Whereas in the abovedescription, second resist PR2 is formed after removing first resist PR1to form constricted parts 19, here, etching is performed again usingfirst resist PR1 to form constricted parts 19.

[0067] By performing etching using first resist PR1, separation grooves41 are formed as shown in FIG. 8(A). By the etching progressing in anisotropic manner, the opening width W2 of the separation grooves isformed more wider than the opening width W1 of first resist PR1. Thus atthe openings of separation grooves 41, the first resist protrudes in aneaves-like manner.

[0068] Referring now to FIG. 8(B), first resist PR1 is then heated tosoften first resist PR1. First resist PR1, which protrudes in aneaves-like manner at the openings of separation grooves 41, is therebymade to cover the side surfaces of separation grooves 41. A structure inwhich just the vicinities of the bottom parts of separation grooves 41are exposed from first resist PR1 is thereby realized.

[0069] By then performing etching again using first resist PR1 as shownin FIG. 8(C), constricted parts 19 are formed and separation grooves 41are formed more deeply. After completion of etching, first resist PR1 isremoved.

[0070] In the second step of this embodiment, circuit elements 12 areaffixed onto the respective mounting parts 45 of the desired conductivepatterns 11 and connection means, electrically connecting the electrodesof circuit elements 12 at the respective mounting parts 45 with thedesired conductive patterns 11, are formed as shown in FIG. 9.

[0071] Circuit elements 12 may be semiconductor elements, such astransistors, diodes, IC chips, etc., or passive elements, such as chipcapacitors, chip resistors, etc. Though the thickness will be greater,face-down semiconductor elements, such as CSP's, BGA's, etc., may alsobe mounted.

[0072] In the third step of this embodiment, molding by insulating resin13 is performed so as to cover circuit elements 12 at the respectivemounting parts 63 in a batch and fill separation grooves 41 as shown inFIG. 10.

[0073] As shown in FIG. 10(A), in this step, insulating resin 13 coverscircuit elements 12 and the plurality of conductive patterns 11, andinsulating resin 13 fills separation grooves 41 between conductivepatterns 11 and fits and binds strongly with the curved structures ofthe side surfaces of conductive patterns 11. Conductive patterns 11 arethus supported by insulating resin 13.

[0074] Also, since constricted parts 19, which are formed to be narrowedin width, are formed in separation grooves 41, the adhesion ofinsulating resin 13 with conductive patterns 11 is made strong by theclose adhesion of insulating resin 13 to constricted parts 19. This stepmay be realized by transfer molding, injection molding, or dipping. Withregard to the resin material, an epoxy resin or other thermosettingresin may be used for transfer molding, or a polyimide resin,polyphenylene sulfide, or other thermoplastic resin may be used forinjection molding.

[0075] An advantage of this step exists in that until covering byinsulating resin 13 is performed, conductive foil 40, which is to becomeconductive patterns 11, is the supporting substrate. Though in therelated art, conductive paths 7 to 11 are formed by employing aninherently unnecessary supporting substrate 5, with the presentembodiment, conductive foil 40, which serves as the supportingsubstrate, is a material that is necessary as an electrode material. Themerit of enabling work to be performed while eliminating the componentmaterials as much as possible is provided and cost reduction can also berealized.

[0076] In the fourth step of this embodiment, the respective conductivepatterns 11 are electrically separated as shown in FIG. 11 and FIG. 12.Two methods may be considered for separating the respective conductivepatterns. In a first method, the rear surface of conductive foil 40 isremoved in an overall manner until the insulating resin 13 that isfilled in separation grooves 41 becomes exposed, and in a second method,conductive foil 40 is removed selectively at locations at whichseparation grooves 41 are provided.

[0077] Referring now to FIG. 11, the first method of separatingconductive patterns 11 shall be described. Here, the rear surface ofconductive foil 40 is removed until the insulating resin 13 that isfilled in the deeply formed separation grooves 41 becomes exposed inorder to separate the respective conductive patterns 11. In this step,the rear surface of conductive foil 40 is removed chemically and/orphysically to separate it into conductive patterns 11. This step iscarried out by lapping, grinding, etching, metal vaporization by alaser, etc. Since separation grooves 41 are formed deeply, conductivepatterns 11 can also be formed deeply here. Specifically, the conductivepatterns can be formed thickly to approximately 150 μm.

[0078] Referring now to FIG. 12, the second method of separatingconductive patterns 11 shall be described. Here, after forming a resistat the rear surface of conductive foil 40 at locations except thelocations corresponding to separation grooves 41, etching is performedfrom the rear surface of conductive foil 40. By performing etching untilthe insulating resin 13 filled in separation grooves 41 becomes exposed,the respective conductive patterns 11 are separated electrically.Conductive patterns 11 that are even thicker than those formed by theabove-described first method can be formed with this method, andspecifically, conductive patterns 11 with a thickness of approximately250 to 300 μm can be obtained.

[0079] By then performing rear surface treatment of conductive patterns11, the final structure shown in FIG. 1 and FIG. 2 is obtained. That is,by coating soft solder or other conductive material onto the exposedconductive patterns 11 as necessary, rear surface electrodes 15 areformed to complete the circuit device.

[0080] In the fifth step of this embodiment, insulating resin 13 isdiced according to the respective mounting parts 45 as shown in FIG. 13.

[0081] In this step, the insulating resin 13 in separation grooves 41 isdiced along dicing lines between the respective mounting parts 45 by adicing blade 49 to perform separation into individual circuit devices.

[0082] In this step, since only the insulating resin 13 filled inseparation grooves 41 exist at the dicing lines, the wear of dicingblade 69 is low and an advantage of enabling dicing to extremelyaccurate external shapes without formation of metal burrs is provided.

What is claimed is:
 1. A circuit device comprising: conductive patternsseparated by separation groove; circuit element, affixed onto theconductive pattern; and an insulating resin, covering the circuitelements and the conductive patterns and filling the separation grooveswhile exposing the rear surfaces of the conductive patterns; whereinconstricted part is formed at side surface of the separation groove andthe insulating resin is adhered to the constricted part.
 2. The deviceof claim 1, wherein the thickness of the conductive patterns is madethicker than the width of the separation groove.
 3. The device of claim1, wherein the constricted part are formed continuously across sidesurface of the separation grooves.
 4. The device of claim 1, wherein therear surface and part of the side surface of the conductive patterns areexposed from the insulating resin.
 5. The device of claim 1, wherein theseparation groove is formed of a first separation groove formed by afirst time of etching and a second separation groove formed by a secondtime of etching, with the cross section of the second separation groovebeing greater than the cross section of the first separation groove. 6.A circuit device comprising: conductive patterns separated by separationgroove; circuit element, affixed onto the conductive pattern; and aninsulating resin, covering the circuit element and the conductivepatterns and filling the separation groove while exposing the rearsurfaces of the conductive patterns; wherein the separation groove isformed of a plurality of grooves formed by etching a plurality of times.7. The device of claim 6, wherein the thickness of the conductivepatterns is made thicker than the width of the separation groove.
 8. Thedevice of claim 6, wherein the rear surface and part of the side surfaceof the conductive patterns are exposed from the insulating resin.
 9. Thedevice of claim 6, wherein the separation groove is formed of a firstseparation groove formed by a first time of etching and a secondseparation groove formed by a second time of etching, with the crosssection of the second separation groove being greater than the crosssection of the first separation groove.
 10. A circuit devicemanufacturing method comprising: forming conductive patterns by formingseparation grooves at locations of a conductive foil except locationsthat are to be the conductive patterns; positioning circuit element onthe conductive pattern; and forming an insulating resin so as to coverthe circuit element and fill the separation groove; wherein constrictedpart is formed on side surfaces of the separation grooves by a pluralityof times of etching and the insulating resin is adhered to theconstricted part.
 11. The method of claim 10, wherein the separationgroove is formed by forming a first resist on the surface of theconductive foil so as to cover regions to be the conductive patterns andthen performing etching, and the separation groove is formed deeply toform the constricted part by exposing the bottom part of the separationgrooves, forming a second resist on the surface of the conductive foil,and performing etching again.
 12. The method of claim 11, wherein thesame mask as the mask used for exposure of the first resist is used forexposure of the second resist to make the second resist remain on sidesurface of the separation groove.
 13. The method of claim 11, whereinthe opening width of the second resist is made narrower than the openingwidth of the first resist to make the second resist remain on sidesurface of the separation grooves.
 14. The method of claim 10, whereinthe separation groove is formed by forming a first resist on the surfaceof the conductive foil so as to cover regions to be the conductivepatterns and then performing etching, and after covering side surface ofthe separation groove by the first resist softened by heating, etchingis performed again.
 15. The method of claim 11, wherein the secondresist is formed by vacuum lamination.
 16. The method of claim 10,wherein the rear surface of the conductive foil is removed until theinsulating resin filling the separation groove becomes exposed.
 17. Themethod of claim 10, wherein the rear surface of the conductive foil isremoved selectively at locations at which the separation groove isprovided until the insulating resin filling the separation groovebecomes exposed.